1. Field of the Invention
The present invention relates to the field of digital information transmission, and more particularly, to an apparatus and method for easily transferring digital video and audio information which is stored in a digital versatile disc (DVD) to a variety of apparatuses having different transfer standards.
2. Description of the Related Art
Among large capacity recordable/reproducible recording media, DVDs store not only audio information and video information but also image information such as a subpicture. The subpicture must be overlaid onto a video signal to be displayed on a screen. Thus, other apparatuses connected to a DVD system (e.g., a DVD player) must also receive both video information and subpicture information to be able to express both the video and the subpicture. To do this, in the prior art, video information and subpicture information decoded by a video decoder and a subpicture decoder, respectively, in a DVD player are overlaid to generate mixed image information, and the mixed image information is again compressed in a moving picture expert group (MPEG) or digital video (DV) format, and then finally transferred. Alternatively, compressed video information and compressed subpicture information from the DVD player are overlaid in an apparatus which receives them, and are then displayed.
In the first method, video information stored in a DVD is decoded by an MPEG-2 video decoder and stored in a video frame memory, and the decoded video signal is again compressed and coded using a compression scheme such as MPEG-2 or DV, and then transferred as an MPEG-2 transport stream (TS) packet format. When a user wishes to view a subpicture, subpicture information is decoded by a subpicture decoder, and then the obtained bitmap image overwrites a designated portion of a video frame memory in which the decoded video signal is stored, and the mixed image is again compressed and transferred.
In the second method, video information and audio information stored in the DVD are converted from a compressed state into an MPEG-2 TS packet format, and then transferred to other apparatuses. In the meantime, subpicture information is transferred in a decoded state or in its original state from the DVD player via a special channel or may be decoded in an apparatus which receives the subpicture information in its original state. At this time, in the apparatus which receives the DVD information, decoded subpicture information and a decoded video signal are mixed and displayed on a screen.
However, in the first method of transferring image information, the compression ratio upon re-encoding to only an MPEG-2 intra (I) picture is lower than that in full MPEG-2 encoding, so that a required bandwidth greatly increases. Thus, if the bandwidth of an information transmission channel is narrow or the information processing speed of an apparatus for receiving information is not sufficient for the bandwidth and bit rate required upon re-encoding, MPEG-2 I picture transmission is impossible. Also, during re-encoding, the quality of an image is unavoidably degraded.
The second method is advantageous in that the quality of original image information, the quality of original audio information, and a transmission bandwidth can be maintained, but is disadvantageous in that a DVD player or an apparatus for receiving DVD information requires a complicated subpicture processing circuit for controlling decoding and displaying of subpicture information, in order to transfer and receive the subpicture information. Therefore, apparatuses which do not have complicated subpicture processing circuits cannot transfer subpicture information.
To solve the above problem, an objective of the present invention is to provide a transferring apparatus and method by which digital versatile disc (DVD) information can be transferred regardless of the function and configuration of an apparatus for receiving the transferred DVD information.
Another objective of the present invention is to provide an apparatus and method by which all apparatuses for receiving DVD information can view DVD information, by transferring DVD information after its transmission format has been appropriately altered according to the requirements of a user, the bandwidth of a transmission channel, and the information processing capability of an apparatus for receiving information (e.g., bit rate and existence or non-existence of a subpicture processing circuit), in order to provide the best quality of image and sound of the DVD information to a user.
To achieve the above objectives, there is provided an apparatus for transferring disc information to another apparatus, including: a stream format converter for providing a first stream by converting the program stream format of audio and video information read from the disc into a transport stream format; a re-encoder for providing a second stream by overlaying video information read from the disc with subpicture information read from the disc and re-encoding the overlaid information using a predetermined compression encoding scheme for image information; and a stream selector for selecting either the first or second stream according to the requirements of a user, the bandwidth of a transmission channel, and the information processing capability of an apparatus for receiving information, and transferring a selected stream to the apparatus for receiving information via a transmission channel.
To achieve the above objectives, there is provided a method of transferring disc information to another apparatus, including: (a) providing a first stream by converting from a program stream format of audio and video information read from a disc into a transport stream format; (b) providing a second stream by overlaying video information read from the disc with subpicture information read from the disc and re-encoding the overlaid information using a predetermined compression encoding scheme for image information; and (c) selecting either the first or second stream according to the requirements of a user, the bandwidth of a transmission channel, and the information processing capability of an apparatus for receiving information, and transferring a selected stream to the apparatus for receiving information via a transmission channel.